Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> writes: > The patch titled > Subject: kthread: Unify kernel_thread() and user_mode_thread() > has been added to the -mm mm-nonmm-unstable branch. Its filename is > kthread-unify-kernel_thread-and-user_mode_thread.patch Andrew. My fuzzy memory thinks Linus asked for the current split. Plus this change just obfuscates the code making the most important detail the argument to a boolean parameter. Meaning you have to have an interface that has only 3 callers memorized to even begin to make sense of it. There are only about 3 callers so *shrug* it can be messed up and we won't hurt much. But ick. Eric > This patch will shortly appear at > https://git.kernel.org/pub/scm/linux/kernel/git/akpm/25-new.git/tree/patches/kthread-unify-kernel_thread-and-user_mode_thread.patch > > This patch will later appear in the mm-nonmm-unstable branch at > git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm > > Before you just go and hit "reply", please: > a) Consider who else should be cc'ed > b) Prefer to cc a suitable mailing list as well > c) Ideally: find the original patch on the mailing list and do a > reply-to-all to that, adding suitable additional cc's > > *** Remember to use Documentation/process/submit-checklist.rst when testing your code *** > > The -mm tree is included into linux-next via the mm-everything > branch at git://git.kernel.org/pub/scm/linux/kernel/git/akpm/mm > and is updated there every 2-3 working days > > ------------------------------------------------------ > From: Huacai Chen <chenhuacai@xxxxxxxxxxx> > Subject: kthread: Unify kernel_thread() and user_mode_thread() > Date: Sat, 3 Jun 2023 09:53:02 +0800 > > Commit 343f4c49f2438d8 ("kthread: Don't allocate kthread_struct for init > and umh") introduces a new function user_mode_thread() for init and umh. > > init and umh are different from typical kernel threads since the don't > need a "kthread" struct and they will finally become user processes by > calling kernel_execve(), but on the other hand, they are also different > from typical user mode threads (they have no "mm" structs at creation > time, which is traditionally used to distinguish a user thread and a > kernel thread). > > So I think it is reasonable to treat init and umh as "special kernel > threads". Then let's unify the kernel_thread() and user_mode_thread() > to kernel_thread() again, and add a new 'user' parameter for init and > umh. > > This also makes code simpler. > > Link: https://lkml.kernel.org/r/20230603015302.1768127-1-chenhuacai@xxxxxxxxxxx > Signed-off-by: Huacai Chen <chenhuacai@xxxxxxxxxxx> > Cc: Eric W. Biederman <ebiederm@xxxxxxxxxxxx> > Cc: Kees Cook <keescook@xxxxxxxxxxxx> > Cc: Luis Chamberlain <mcgrof@xxxxxxxxxx> > Signed-off-by: Andrew Morton <akpm@xxxxxxxxxxxxxxxxxxxx> > --- > > include/linux/sched/task.h | 3 +-- > init/main.c | 4 ++-- > kernel/fork.c | 20 ++------------------ > kernel/kthread.c | 2 +- > kernel/umh.c | 6 +++--- > 5 files changed, 9 insertions(+), 26 deletions(-) > > --- a/include/linux/sched/task.h~kthread-unify-kernel_thread-and-user_mode_thread > +++ a/include/linux/sched/task.h > @@ -100,8 +100,7 @@ struct task_struct *copy_process(struct > struct task_struct *create_io_thread(int (*fn)(void *), void *arg, int node); > struct task_struct *fork_idle(int); > extern pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name, > - unsigned long flags); > -extern pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags); > + unsigned long flags, bool user); > extern long kernel_wait4(pid_t, int __user *, int, struct rusage *); > int kernel_wait(pid_t pid, int *stat); > > --- a/init/main.c~kthread-unify-kernel_thread-and-user_mode_thread > +++ a/init/main.c > @@ -690,7 +690,7 @@ noinline void __ref __noreturn rest_init > * the init task will end up wanting to create kthreads, which, if > * we schedule it before we create kthreadd, will OOPS. > */ > - pid = user_mode_thread(kernel_init, NULL, CLONE_FS); > + pid = kernel_thread(kernel_init, NULL, NULL, CLONE_FS, true); > /* > * Pin init on the boot CPU. Task migration is not properly working > * until sched_init_smp() has been run. It will set the allowed > @@ -703,7 +703,7 @@ noinline void __ref __noreturn rest_init > rcu_read_unlock(); > > numa_default_policy(); > - pid = kernel_thread(kthreadd, NULL, NULL, CLONE_FS | CLONE_FILES); > + pid = kernel_thread(kthreadd, NULL, NULL, CLONE_FS | CLONE_FILES, false); > rcu_read_lock(); > kthreadd_task = find_task_by_pid_ns(pid, &init_pid_ns); > rcu_read_unlock(); > --- a/kernel/fork.c~kthread-unify-kernel_thread-and-user_mode_thread > +++ a/kernel/fork.c > @@ -2958,7 +2958,7 @@ pid_t kernel_clone(struct kernel_clone_a > * Create a kernel thread. > */ > pid_t kernel_thread(int (*fn)(void *), void *arg, const char *name, > - unsigned long flags) > + unsigned long flags, bool user) > { > struct kernel_clone_args args = { > .flags = ((lower_32_bits(flags) | CLONE_VM | > @@ -2967,23 +2967,7 @@ pid_t kernel_thread(int (*fn)(void *), v > .fn = fn, > .fn_arg = arg, > .name = name, > - .kthread = 1, > - }; > - > - return kernel_clone(&args); > -} > - > -/* > - * Create a user mode thread. > - */ > -pid_t user_mode_thread(int (*fn)(void *), void *arg, unsigned long flags) > -{ > - struct kernel_clone_args args = { > - .flags = ((lower_32_bits(flags) | CLONE_VM | > - CLONE_UNTRACED) & ~CSIGNAL), > - .exit_signal = (lower_32_bits(flags) & CSIGNAL), > - .fn = fn, > - .fn_arg = arg, > + .kthread = !user, > }; > > return kernel_clone(&args); > --- a/kernel/kthread.c~kthread-unify-kernel_thread-and-user_mode_thread > +++ a/kernel/kthread.c > @@ -400,7 +400,7 @@ static void create_kthread(struct kthrea > #endif > /* We want our own signal handler (we take no signals by default). */ > pid = kernel_thread(kthread, create, create->full_name, > - CLONE_FS | CLONE_FILES | SIGCHLD); > + CLONE_FS | CLONE_FILES | SIGCHLD, false); > if (pid < 0) { > /* Release the structure when caller killed by a fatal signal. */ > struct completion *done = xchg(&create->done, NULL); > --- a/kernel/umh.c~kthread-unify-kernel_thread-and-user_mode_thread > +++ a/kernel/umh.c > @@ -130,7 +130,7 @@ static void call_usermodehelper_exec_syn > > /* If SIGCLD is ignored do_wait won't populate the status. */ > kernel_sigaction(SIGCHLD, SIG_DFL); > - pid = user_mode_thread(call_usermodehelper_exec_async, sub_info, SIGCHLD); > + pid = kernel_thread(call_usermodehelper_exec_async, sub_info, NULL, SIGCHLD, true); > if (pid < 0) > sub_info->retval = pid; > else > @@ -169,8 +169,8 @@ static void call_usermodehelper_exec_wor > * want to pollute current->children, and we need a parent > * that always ignores SIGCHLD to ensure auto-reaping. > */ > - pid = user_mode_thread(call_usermodehelper_exec_async, sub_info, > - CLONE_PARENT | SIGCHLD); > + pid = kernel_thread(call_usermodehelper_exec_async, sub_info, > + NULL, CLONE_PARENT | SIGCHLD, true); > if (pid < 0) { > sub_info->retval = pid; > umh_complete(sub_info); > _ > > Patches currently in -mm which might be from chenhuacai@xxxxxxxxxxx are > > kthread-unify-kernel_thread-and-user_mode_thread.patch
